Various devices and methods for measuring pressures of fluid media such as gases and liquids are available in the related art. The measuring variable pressure is a nondirectional force that occurs in gases and liquids and acts in all directions. Dynamically and statically acting measuring-value pickups or sensor elements are available for measuring the pressures. Dynamically acting pressure sensors are used only for measuring pressure pulsations in gaseous or liquid media. The pressure measurement may be carried out directly, via a diaphragm deformation, or with the aid of a force sensor.
In particular when measuring very high pressures, it would be sufficient simply to expose an electrical resistor to the medium inasmuch as all known resistors exhibit a pressure dependency to a lesser or greater degree. However, the suppression of the simultaneous dependency of the resistors from the temperature and the pressure-tight feeding of their electrical connections out of the pressure medium causes difficulties.
Therefore, the most common method used for measuring pressures first utilizes a thin diaphragm as the mechanical intermediate stage for the signal measurement, which is exposed to the pressure on one side and deforms to a greater or lesser degree under its influence. Within broad limits, its thickness and diameter are able to be adapted to the particular pressure range. Low pressure-measuring ranges lead to comparatively large diaphragms which may deform in the range of 0.1 mm to 1 mm. High pressures, on the other hand, require thicker diaphragms of a small diameter, which frequently deflect only a few micrometers. Such pressure sensors are known, for example, from Konrad Reif (Publisher): Sensoren im Kraftfahrzeug [Automotive Sensors], 1st ed. 2010, pages 80-82 and 134-136.
German Patent Application No. DE 10 2011 085 055 A1 describes a temperature-measuring device for measuring a temperature of a streaming fluid medium, in which a pressure-sensor module may optionally be provided.
German Patent Application No. DE 2012 218 214 A1 describes a pressure sensor for measuring a pressure of a fluid medium, the sensor having a housing and a pressure connector. Two sensor elements that are independent of each other are situated inside the housing. A pressure supply may be implemented via the pressure connector through pressure-supply channels to the sensor elements that measure the applied pressure. In this way, a redundant pressure measurement is able to be ensured in a reliable manner, yet it is impossible to measure the pressure at different locations within the measuring chamber.
European Patent No. EP 1 521 952 B1 describes a device for a pressure measurement, which has a pressure-sensor module that allows for a differential-pressure measurement between two different housing chambers.
In an internal combustion engine, fuel is mixed with air and made to ignite. The chemical energy bound in the fuel is partially converted into mechanical work in the process. Frequently, the air required to combust the fuel is not simply aspirated but is introduced into the combustion chamber by a compressor. The compressor is able to be driven mechanically or driven by the combustion gas (exhaust gas) expelled by the engine (exhaust turbocharger). The fuel to air ratio must lie within a certain range on account of the flammability of the pollutants etc. that are produced during the combustion, and is therefore controlled or regulated as a function of the operating mode.
In order to catch the particle emissions produced in the diesel combustion, a diesel particle filter is installed downstream from the turbine, for instance because of the EU5 exhaust-gas standard. However, the particles accumulated in the diesel particle filter must be removed from the filter again. In other words, the diesel particle filter must be regenerated on a regular basis by increasing the exhaust-gas temperature in the diesel particle filter until the particles are combusted to ash. For the control of the regeneration intervals, a differential pressure sensor is generally installed upstream above the diesel particle filter, which allows for modeling of the loading of the diesel particle filter. Not only fresh air but also exhaust gas is recirculated to the engine in order to reduce the nitrogen oxide emissions. The share of recirculated exhaust gas in the entire intake mass flow, i.e., the recirculation rate, is usually varied as a function of the operating point, e.g., the engine speed, load, temperature, etc. The exhaust gas recirculation may take place directly from the outlet to the intake in the form of a high-pressure exhaust-gas recirculation of the engine, or from a point downstream from the turbine and the diesel particle filter to a point upstream from the compressor in the form of a low-pressure exhaust-gas recirculation. To protect the compressor from damage caused by particles, a diesel particle filter must be installed upstream from a branch-off of a low-pressure exhaust recirculation system. While the high-pressure exhaust recirculation has been established for a long time in diesel engines, the low-pressure exhaust recirculation is a relatively new approach for satisfying future exhaust regulations. The regulation of the low-pressure exhaust recirculation mass flow or the low-pressure exhaust recirculation rate is therefore of decisive importance. In addition to the fresh air mass flow, the low-pressure exhaust-recirculation mass flow is required in order to calculate the low-pressure exhaust recirculation rate. In passenger cars, the fresh air mass flow is generally measured with the aid of a sensor, e.g., an air-mass meter or a hot-film air-mass meter. The low-pressure exhaust recirculation mass flow is normally estimated via a differential pressure sensor over the low-pressure exhaust recirculation section, i.e., between the low-pressure branch-off downstream from the diesel particle filter and the low-pressure mixing location upstream from the compressor. The low-pressure exhaust recirculation section is modeled as a throttle.
Despite the improvements brought about by these pressure sensors, there is still potential for optimizing conventional pressure sensors. For example, a measurement of a differential pressure via the diesel particle filter and the differential pressure via the low-pressure exhaust recirculation line at present requires two separate pressure sensors, each having its own voltage supply and its own supply hoses.